Computed tomography (CT) systems are effective to provide data from the interiors of the body which can be reduced to displays without the complications of superimposed detail normally inherent in traditional x-ray pictures. For example, CT scanners are in widespread use providing brain information that is very useful both in diagnosis and treatment. Details of the structure and operation of such scanners are provided in U.S. Pat. No. 3,106,640 issued Oct. 8, 1963, and entitled "Radiant Energy Apparatus for Investigating Selected Areas of the Interior of Objects Obscured by Dense Material".
A CT scan might, for example, be taken of a patient evidencing symptoms of a brain tumor. Essentially, the actual information is representative of a plurality of individual data planes or scan slices which are taken through the brain and are somewhat parallel, depending upon the degree to which the patient's head may have moved between the individual scans. Studying the scan slices, the trained physician or the like may observe the presence and approximate location of a tumor. With such information, a variety of treatments might be effectively executed, several of which involve placing an instrument or probe into the brain so that the probe tip is at the tumor or target location.
Although the CT scanner provides exceedingly valuable information, a problem has remained of accurately defining the position of the target with respect to an accessible reference location for accurately placing a therapeutic probe. At least one locating method has been proposed and was described in the American Journal of Roentgenology, Volume 127, pages 167-170, 1976, by Bergstrom and Greitz entitled "Stereotaxic Computed Tomography". However, such prior technique requires that the patient's head be fixed to the CT scanner to preserve the reference. Such a requirement not only imposes considerable discomfort on the patient, but results in other inconveniences, particularly if surgical procedures are involved. Consequently, a need exists for a system utilizing a CT scanner to locate and reach internal maladies which system does not rely upon a mechanically fixed relationship between the patient and the CT scanner. Such a system is needed that will enable the accurate and reproducible location of a target point and which facilitates the determination of a path to a target as well as providing for guidance of a probe along such a path.
In general, the present invention includes a stereotactic frame which is affixed to the patient, yet will allow the patient freedom of motion and relative comfort. The stereotactic frame cooperates with the CT scanner to provide data to reference each scan slice to the stereotactic frame. Additionally, the stereotactic frame incorporates a universal holder mechanism for guiding a therapeutic probe to a target. Using the stereotactic frame as an integral component, the system of the present invention also incorporates a CT scanner along with a display apparatus and data processing means for transforming and processing data.
Considering an exemplary use of the system, the stereotactic frame would be fixed to a patient's cranium for cooperative use with a CT scanner to accomplish a brain scan containing reference indicia. At the conclusion of the brain scan, the patient (wearing the stereotactic frame) would be mobile and could move from the CT scanner. The scan slices then would be displayed by the system for study and analysis to determine the presence and location of a tumor (target). The target is indicated to the system (as by a cursor input to a specific scan slice) along with a second point to supplement the data and designate a path for reaching the tumor. Using the reference indicia, the data processing apparatus expresses the path in terms that are referenced to the stereotactic frame. For example, the path may be indicated by position settings or positional indications for the holder mechanism on the stereotactic frame. The computing apparatus in cooperation with the display apparatus then indicates the penetration location of the path through each scan slice. If problem penetrations are indicated, an alternate path is selected. If the path under investigation appears relatively free of complications, the patient is taken to surgery; and using the stereotactic frame, a therapeutic probe is guided to the target with minimal disturbance of tissue along the path.